Thin film capacitor and electronic circuit substrate having the same

Abstract

To provide a thin film capacitor having high adhesion performance with respect to a multilayer substrate. A thin film capacitor includes: a metal foil having a roughened upper surface; a dielectric film covering the upper surface of the metal foil and having an opening through which the metal foil is partly exposed; a first electrode layer contacting the metal foil through the opening; and a second electrode layer contacting the dielectric film without contacting the metal foil. A height of the first electrode layer is lower than a height of the second electrode layer. This enhances adhesion performance when the thin film capacitor is embedded in a multilayer substrate and improves ESR characteristics.

What is claimed is: 
     
       1. A thin film capacitor comprising:
 a metal foil having one roughened main surface; 
 a dielectric film covering the one main surface of the metal foil and having an opening through which the metal foil is partly exposed; 
 a first electrode layer contacting the metal foil through the opening; and 
 a second electrode layer contacting the dielectric film without contacting the metal foil, 
 wherein the first electrode layer is lower in height than the second electrode layer. 
 
     
     
       2. The thin film capacitor as claimed in  claim 1 ,
 wherein the first and second electrode layers are separated from each other by an annular slit, 
 wherein the first electrode layer is provided in a first area surrounded by the slit, and 
 wherein the second electrode layer is provided in a second area positioned outside the slit. 
 
     
     
       3. The thin film capacitor as claimed in  claim 2 , further comprising a first insulating member provided inside the slit and positioned between the first and second electrode layers. 
     
     
       4. The thin film capacitor as claimed in  claim 3 , further comprising a second insulating member provided on the one main surface of the metal foil and surrounding the second electrode layer. 
     
     
       5. The thin film capacitor as claimed in  claim 1 , wherein the second electrode layer includes a first conductive member contacting the dielectric film and made of a conductive polymer material and a second conductive member contacting the first conductive member and made of a metal material. 
     
     
       6. The thin film capacitor as claimed in  claim 5 , wherein the first electrode layer includes a third conductive member contacting the metal foil and made of a conductive polymer material and a fourth conductive member contacting the third conductive member and made of a metal material. 
     
     
       7. The thin film capacitor as claimed in  claim 5 , wherein the first electrode layer includes a fourth conductive member contacting the metal foil and made of a metal material. 
     
     
       8. The thin film capacitor as claimed in  claim 1 , wherein the first electrode layer is lower in height than the second electrode layer by 1 μm or more. 
     
     
       9. The thin film capacitor as claimed in  claim 8 , wherein the first electrode layer is lower in height than the second electrode layer by 2 μm or more. 
     
     
       10. The thin film capacitor as claimed in  claim 1 , wherein a difference in height between the first and second electrode layers is 7 μm or less. 
     
     
       11. The thin film capacitor as claimed in  claim 1 , wherein other main surface of the metal foil is roughened. 
     
     
       12. An electronic circuit substrate comprising:
 a substrate having a wiring pattern; 
 a semiconductor IC provided in the substrate; and 
 the thin film capacitor as claimed in  claim 1  provided in the substrate, 
 wherein the first and second electrode layers of the thin film capacitor are connected to the semiconductor IC through the wiring pattern.